UPDATE - April 14, 5:10 p.m. ET: In a televised speech on Sunday that came in response to the deadly violence in eastern Ukraine, the country's acting president Oleksander Turchinov gave pro-Russian militants until Monday morning to disarm, or face a "full-scale anti-terrorist operation," according to Reuters and other news reports. "The National Security and Defense Council has decided to launch a full-scale anti-terrorist operation involving the armed forces of Ukraine," Turchinov said. "We will not allow Russia to repeat the Crimean scenario in the eastern regions of Ukraine."

The takeover of Ukraine government buildings turned bloody Sunday, as government forces sought to retake a building seized by pro-Russian militants in the eastern city of Sloviansk.

Ukraine Interior Minister Arsen Avakov said one government security officer was killed and four were wounded in what he termed an "anti-terrorist" operation. "There were dead and wounded on both sides," Avakov said, according to Reuters.

The Russian news agency RIA reported that one pro-Moscow activist was killed in the clashes in Sloviansk.

Sloviansk was one of at least five cities where armed pro-Russian separatists had taken over Ukraine government buildings and erected barricades in recent hours. Many of them wore camouflaged uniforms, and carried Kalashnikov rifles identical to those worn and carried by the pro-Russian forces who took control of Crimea a month ago.

Officials in Kiev and Washington said the moves appeared to be orchestrated by Russia, much like how Moscow moved against Crimea.

“We are very concerned by the concerted campaign we see underway in eastern Ukraine today by pro-Russian separatists, apparently with support from Russia, who are inciting violence and sabotage and seeking to undermine and destabilize the Ukrainian state,” Laura Lucas Magnuson, a National Security Council spokesperson, said in a statement. “We saw similar so-called protest activities in Crimea before Russia’s purported annexation. We call on President Putin and his government to cease all efforts to destabilize Ukraine.”

Clashes and bloodshed were also reported on Sunday in the eastern Ukraine city of Kharkiv, as pro-Ukraine and pro-Russia groups held rival demonstrations. Kyiv Post reported that at least three Ukraine supporters were severely beaten by pro-Russia activists.

Pro-Russian protesters also gained access to the regional government administration building in Kharkiv, Kyiv Post reported.

"They were shouting and broke windows, although nobody actually was trying to stop them," said Eugene Maslov, a Kharkiv journalist. They stayed inside the building with the city's mayor, Gennadiy Kernes, according to an Interfax-Ukraine news agency report.

City council in #Kharkiv seized by separatists. Two central metro stations closed after clashes

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